InterNACHI Plumbing Practice Exam

The assertion that rocks or blocks can support drainage piping inside a trench is false. In proper drainage system design, the support for drainage pipes must ensure that they are both stable and capable of maintaining proper alignment. While rocks or blocks might seem like a potential support option, they often do not provide a uniform or stable base for drainage piping.

The primary material used to properly support drainage piping is granular material, such as gravel or sand. These materials allow for proper drainage and prevent settling or shifting of the pipes. They also facilitate the movement of water away from the piping, which is essential for the functionality of a drainage system.

Therefore, for effective and reliable drainage system installation, it is crucial to use recommended materials that are specifically designed for that purpose instead of relying on rocks or blocks, which can lead to improper support and potential plumbing issues.